i have basicly stock 2008 B4000, i found a store that sells the 4 inch superlift cheap. what is the max tire sixe i could fit with a 4 inch suspention lift? also what gear raito would i need for the tires sizes? and how do i change the gear raito?

Yeah OP....33x12.50 comfortably. Run at least an 8" rim, though a 10" rim is suggest for a good wear pattern.

What's your current gear ratio? What transmission? To figure out your current ratio, go to your rear axle and look at the metal tag on the differential cover...it'll look like any of these: 4L10, 3L73, 4 10, 3 73.

If you've got 4.10's now, 33's are perfectly fine with that. If you're 3.73, they'll work, but it won't be that great...it'll make your 3.73's feel like 3.20's when you put the new tires on it....kind of a dog. If you're 3.73, I'd go 4.56:1 gears and have a professional differential or off road shop install them for ya.